Chi-Chuan Kan

Adsorption of indium(III) ions from aqueous solution using chitosan-coated bentonite beads

Batch adsorption study was utilized in evaluating the potential suitability of chitosan-coated bentonite (CCB) as an adsorbent in the removal of indium ions from aqueous solution. The percentage (%) removal and adsorption capacity of indium(III) were examined as a function of solution pH, initial concentration, adsorbent dosage and temperature. The experimental data were fitted with several isotherm models, where the equilibrium data was best described by Langmuir isotherm. The mean energy (E) value was found in the range of 1-8kJ/mol, indicating that the governing type of adsorption of indium(III) onto CCB is essentially physical. Thermodynamic parameters, including Gibbs free energy, enthalpy, and entropy indicated that the indium(III) ions adsorption onto CCB was feasible, spontaneous and endothermic in the temperature range of 278-318K. The kinetics was evaluated utilizing the pseudo-first order and pseudo-second order model. The adsorption kinetics of indium(III) best fits the pseudo-second order (R(2)>0.99), which implies that chemical sorption as the rate-limiting step.

Adsorption of Mn2+ from aqueous solution using Fe and Mn oxide-coated sand

The adsorption of Mn2+ onto immobilized Mn-oxide and Fe-oxide adsorbent such as manganese oxide-coated sandl (MOCS1), manganese oxide-coated sand2 (MOCS2), iron oxide-coated sand2 (IOCS2), and manganese and iron oxide-coated sand (MIOCS) was investigated. The effects of pH (5.5 to 8.0) and temperature (25 to 45 degrees C) on the equilibrium capacity were examined. Equilibrium studies showed that there is a good fit with both Freundlich and Langmuir isotherm, which indicates surface heterogeneity and monolayer adsorption of the adsorbents. Kinetic data showed high correlation with the pseudo second-order model, which signifies a chemisorption-controlled mechanism. The activation energies, activation parameters (deltaG, deltaH, deltaS), and thermodynamic parameters (deltaG0, deltaH0, deltaS0) confirmed that adsorption with MIOCS was endothermic and more spontaneous at higher temperature while an opposite trend was observed for the other adsorbents. Thermodynamic studies showed that adsorption involved formation of activated complex, where MOCS 1 and MIOCS follow a physical-chemical mechanism, while MOCS2 and IOCS2 follows purely chemical mechanism.

Removal of manganese(II) and iron(II) from synthetic groundwater using potassium permanganate

ABSTRACTThe removal of Mn2+ and Fe2+ from synthetic groundwater via oxidation using potassium permanganate was investigated. Batch jar tests were carried out under a constant pH of 8.0, where the effect of parameters such as the oxidant dose, presence of co-ions (Ca2+, Mg2+) and alum addition on the removal of Mn2+ and Fe2+ was examined. The partial removal of Mn2+ using aeration in single and dual metal system was 30.6% and 37.2%, respectively. The oxidant dose of 0.603 mg/L KMnO4 was the minimum amount needed to reduce Mn2+ below its maximum contaminant level. The presence of Fe2+ improved the removal of Mn2+ due to the autocatalytic effect of hydrous manganese-iron oxide, where its presence was confirmed by digital microscopy and EDX. The presence of Ca2+ and Mg2+ as well as the alum addition after oxidation has a negative effect on the removal of Mn2+. The removal mechanism of Mn2+ and Fe2+ was a combination of oxidation and adsorption or co-precipitation between the hydrous oxide and the dissolved me...

Adsorption of Copper (II) by Chitosan Immobilized on Sand

Because of the dramatic develop of industry, heavy metal pollution has become a global environmental considerations. The heavy metals in the soil and groundwater have endangered our environment and human body by direct or indirect pathway. Thus, how to solve efficiently the heavy metal pollution in groundwater has become the most essential issue around the world. Theoretically, the traditional remediation method is physicalchemical processes, which resulted in high capital cost and serious damage in contaminated sites. Currently, bioremediation is a developing biologic process that offers the possibility to destroy or render harmless various contaminants using natural biological activity. As such, it uses relatively low-cost, low-technology techniques, which generally have a high public acceptance and can often be carried out on site. Biopolymer is a biodegradable material, and becomes a newly developing tendency for many industries. Those materials can be degraded by landfill process, which provides the nutrient for microorganisms, plants and animals. Based on this concept, obtaining form insects, the shell of aquatic crustaceans (crab and shrimp), and the cell wall of fungus. Chitin and Chitosan have widely applied in the adsorption study of heavy metal based on their chemical structures, reaction characteristics and modification properties. This research is based on the ideal of green design and using biodegradable material (chitosan) coated with sand. Nature materials such as sand, soil, clay and chitosan used as adsorbent to examine by Cu(superscript 2+) adsorption capability and isotherms analysis using Langmuir isotherm. In the considerations of real scale and cost-effective applications, sand was immobilization on chitosan to uptake the Cu(superscript 2+) ions in aqueous solution. Moreover, the adsorption capacity of 5% chitosan-coated sand (10.87 mg/g) was a better adsorbent compared to chitosan used alone (7.55 mg/g), 1% (3.38 mg/g) and 2.5% (4.50 mg/g) weight percentages coasted with chitosan. It is suggested that using 5 % chitosan-coated sand as a bioadsorbent in wastewater treatment process.

Feasibility studies on arsenic removal from aqueous solutions by electrodialysis

The effectiveness of electrodialysis (ED) in removing inorganic arsenic (As) from aqueous solution was investigated. A tailor-made ED stack was used to perform current-voltage and optimization experiments in a recirculating batch mode. Samples were pre-oxidized with NaClO using 1:2 sample to oxidant weight ratio (RS:O) to transform 100% of As(III) to As(V) in 180 seconds. A high feed water conductivity of 1500 μS/cm and a low feed water conductivity of 800μS/cm had limiting currents of 595 mA and 525 mA, respectively. Optimum experimental conditions that provided maximum As separation were applied potential (E) of 12 V, feed flow rate (Q) of 0.033 L/s, feed concentration (C) of 662.0 μg L−1, and operating time (t) of 45 min, the most significant ones were applied potential, feed concentration and operating time. Model confirmation experiments showed a good agreement with experimental results with only 0.031% error. The total As in the diluate stream was 4.0 μg L−1, consisting of an average of 3.0 μg L−1 As(V) and 1.0 μg L−1 As(III).

Ultrasound irradiation combined with hydraulic cleaning on fouled polyethersulfone and polyvinylidene fluoride membranes

In this study, an ultrasonic irradiation technique was utilized to mitigate the fouling of polyethersulfone (PES) and polyvinylidene fluoride (PVDF) membranes. The use of ultrasound at 20 kHz was applied to a dead-end microfiltration cell in order to mitigate fouling caused by the presence of colloidal bentonite particles. The effect of ultrasonic power and pulse duration on the permeate flux recovery was examined. Measurements indicate that an increase in ultrasonic power and longer pulse duration results to a higher permeate flux recovery. In order to reduce power consumption, a low to high power shift (LHPS) and pulsation method, were investigated. Methods of cleaning such as ultrasonic irradiation, ultrasonic cleaning with forward flushing and ultrasonic cleaning with backwashing were utilized and their cleaning efficiencies were examined. The cleaning performance was assessed using the clean water flux method and scanning electron microscope analysis of the cleaned membranes. Results showed that LHPS and pulsation method both improve the permeate flux recovery but were not able to attain the 93.97 and 74.88% flux recovery for PES and PVDF that was achieved by constant-15 W ultrasonic cleaning. In addition, forward flushing and backwashing may enhance the performance of ultrasonic cleaning at 9 W but could become disadvantageous at 15 W.

Fouling Elimination of PTFE Membrane under Precoagulation Process Combined with Ultrasound Irradiation

Precoagulation is one of the effective pretreatments in membrane filtration. This process mitigates membrane fouling, which is the major drawback of membrane technology in drinking water and wastewater treatment. This study investigated the effects of precoagulation under different coagulation mechanisms on membrane fouling. Use of ultrasound in polytetrafluoroethylene (PTFE) membrane cleaning was also evaluated. In precoagulation, synthetic raw water was precoagulated using aluminum sulfate at different coagulation mechanisms, named electrostatic patch effect (EPE), charge neutralization (CN), and sweep flocculation (SW). Flocs produced from different coagulation mech- anisms exhibited different sizes, structures, and strengths. Likewise, the fouling type generated from each mechanism was demonstrated as pore blocking for EPE, cake formation for SW, and combination phenomenon for CN. Moreover, this study indicated that the membrane flux was enhanced in the sequence of EPE > CN > SW. The flux recovery rate after ultrasonic cleaning was in the sequence of SW > CN > EPE. Finally, this study evidenced that the floc characteristics from various coagulation mechanisms affected membrane per- formance, fouling types, and ultrasonic cleaning efficiency. DOI: 10.1061/(ASCE)EE.1943-7870.0000406.

Removal of manganese ions from synthetic groundwater by oxidation using KMnO4 and the characterization of produced MnO2 particles

The aim of this study is to investigate the conditions for the removal of manganese ions from synthetic groundwater by oxidation using KMnO(4) to keep the concentration below the allowed level (0.05 mg/L). The process includes low-level aeration and addition of KMnO(4) in a Jar test system with Mn(2 + ) concentration of 0.50 mg/L, similar to that of natural groundwater in Taiwan. Different parameters such us aeration-pH, oxidant dose, and stirring speed were studied. Aeration alone was not sufficient to remove Mn(2 + ) ions completely even when the pH was increased. When a stoichiometric amount of KMnO(4) (0.96 mg/L) was used, a complete Mn(2 + ) removal was achieved within 15 min at an optimum pH of 8.0. As the amount of KMnO(4) was doubled, lower removal efficiency was obtained because the oxidant also generated manganese ions. The removal of Mn(2 + ) ions could be completed at pH 9.0 using an oxidant dose of 0.48 mg/L because Mn(2 + ) could be sorbed onto the MnO(2) particles. Finally, The MnO(2) particles were characterized using scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX).

Manganese and iron recovery from groundwater treatment sludge by reductive acid leaching and hydroxide precipitation

In this study, the recovery of manganese (Mn) and iron (Fe) from groundwater treatment sludge through reductive acid leaching and hydroxide precipitation was investigated. Maximum leached Mn (100%) was obtained using sulfuric acid and hydrogen peroxide at 25 °C. Leached Mn and Fe decreased with the increase in the solid-liquid ratio. Leaching time had minimal effect on Mn and Fe leaching beyond 5 min, while agitation rate had minimal effect beyond 150 rpm. At 25 °C, the rate-limiting step of Mn leaching was diffusion through inert solid components of the sludge, composed mainly of insoluble sand particles. Fe leaching was governed by diffusion through the insoluble components of the sludge, including the unreacted manganese dioxide (MnO2). Maximum precipitation of Fe and separation from Mn in the leachate through addition of potassium hydroxide occurred at pH 4.0. The results demonstrated that reductive acid leaching and hydroxide precipitation is an effective means of recovering Mn and Fe from groundwater treatment sludge. The applicability of the recovered Mn for nickel ion removal from aqueous solution was also explored in the study. Highest nickel ion uptake by the MnO2 synthesized from the recovered Mn was at 111.67 mg g-1, even exceeding the adsorption capacities of previously studied nickel adsorbents.